Chemical and Electrical Instability of MgxZn1-xO in CdTe Thin Film Solar Cell

MgxZn1-xO (MZO) is a promising window material for high-efficiency CdTe thin film solar cell fabrication. However, the performance of MZO-based CdTe solar cell exhibits high sensitivity to the heat treatment of MZO during device fabrication process. In this article, the chemical, microstructural and electrical instability of MZO films and their effect on device performance of CdTe thin film solar cell was studied. It is found that during the high-temperature vacuum treatment (400 degrees C-600 degrees C), the atomic element losses in the MZO films led to high oxygen-vacancy concentration and formation of an Mg-rich surface layer. The high-temperature treated MZO films exhibited rough surface morphology, high electronic conductivity, and low electron affinity. The rough MZO surface induced formation of trap states with high concentration in the CdTe absorber and decreased open-circuit voltage for the solar cell. The MZO conductivity and the surface electron affinity affect the carrier transport in the solar cells. This work demonstrates that the heat treatment process of the MZO window layer significantly affects the performance and reproducibility of CdTe solar cell fabrication.

Automated summary

The study reveals that the instability of MZO films during high-temperature treatment affects the performance of CdTe solar cells, mainly manifested as increased oxygen-vacancy concentration, formation of Mg-rich surface layer, and trap states in the CdTe absorber.